Google has added the ability to unsend messages as a formal feature in Gmail. It had previously been available in experimental form and still has only a limited use.

The feature originally appeared in Gmail Labs, an optional setting on Gmail that lets you try out ideas Google is still developing, with the associated disclaimer about things breaking. It was then recently added to Inbox by Gmail, a mobile app with some additional features not found in the main Gmail site and app.

In the next two weeks or so, you’ll be able to switch on the feature on the Gmail website by clicking the gear icon and selecting Settings from the drop-down menu. “Undo Send” will then be listed among the options in the General section.

After switching it on, you’ll be able to select a cancellation period of 5, 10, 20 or 30 seconds. That’s a clue as to how the feature can work regardless of the recipient or their chosen email provider. Rather than you being able to recall a sent message from the recipient’s inbox, the feature simply delays every outgoing message for the chosen period, allowing you to cancel the message during the delay.

Once the feature is switched on, you’ll see an “Undo” link appear on the screen alongside the usual “Your message has been sent” confirmation.

If you were already using the feature in Gmail Labs, it should be switched on by default in Gmail itself as soon as the feature is added.